The recent advancement of computer-based numerical analysis has enabled reproduction of various phenomena in a heart by modeling it on a computer. For example, the behavior of myocardium is analyzed numerically and reproduced on a monitor screen with the techniques of three-dimensional computer graphics. It is also possible to produce an electrocardiogram on the thorax of a person as an outcome of simulation. Such output data representing electrical activities in a heart may be visualized as video images, along with other data indicating the propagation of cardiac excitation.
Electrocardiograms are used as source data for analysis of arrhythmia and other heart diseases. For example, one proposed electrocardiogram analyzer evaluates electrical activities in a heart in terms of the distribution of indicators that are useful for prediction of fatal arrhythmias. Also, several researchers have proposed a method for classifying waveforms of Holter electrocardiography by using clustering techniques. See, for example, the following documents:
Japanese Laid-open Patent Publication No. 2007-313122
Tsuyunashi, Oguri, Matsuo, Iwata, “The Holter ECG waveform classification using clustering,” The Institute of Electronics, Information and Communication Engineers (IEICE), Technical Report of IEICE. MBE, ME and Biocybernetics, Dec. 1, 2003, 103(489), pp. 23-28
A patient suspected of having a heart disease is subjected to monitoring of electrical signals produced in his or her myocardium, and the result is obtained as electrocardiogram data. There is a need in some situations for visually checking the behavior of the heart in comparison with electrocardiogram data. This is achieved by conducting a dynamic simulation of myocardial motion and blood flows and reproducing the simulated heart behavior in the form of a three-dimensional model on a monitor screen.
It is not easy, however, for the conventional tools to make a simulation result exactly simultaneous with electrocardiogram data because of their difference in the progress of time. More specifically, existing electrocardiogram data is used as input data for a behavioral simulation of myocardium, where the electrocardiogram data provides particular conditions about propagation of excitation in the patient's heart. The simulation process produces a set of output data indicating the state of the heart at each discrete time step. There is, however, some amount of time difference between the generation of electrical signals seen in the electrocardiogram and the consequent contraction of myocardium. Because of this time difference, simply starting an electrocardiogram together with animation of a heart beat would not be sufficient for achieving correct synchronization between the variations of electrical signal strength and the motion of cardiac muscle.